Pregnancy? Please help. 🙁😔

So me and my boyfriend had sex on the 20th and he didn't pee after ejaculation the first time he pulled out before cuming the second time. We didn't use a condom either times . I didn't take plan B. It was on one of tmr fertile days too. I don't take birth control and stuff. I experienced lower back pain once or twice but that's pretty much it and I took a urine pregnancy test on the 30th. I haven't experience any symptoms of pregnancy though. Could I still be pregnant? The test said I was not pregnant. Could I still be? My period is very irregular. What do I do?? I've been extremely stressed about this. Please help.